Touch screens are prevalent in today's computing environment. Portable computers, desktop computers, tablets, smart phones, and smartwatches typically employ a touch screen to gain user input for navigation and control of these devices. Thus, discerning the intent of the user via touch inputs is an important feature of a touch screen device.
Touch screens typically operate based on capacitive touch sensing, and include a patterned array of conductive features. For instance, the patterned array of conductive features may include sets of lines, conductive pads, overlapping structures, interleaved structures, diamond structures, lattice structures, and the like. By evaluating changes in capacitance at different lines or sets of lines, a user touch or hover, such as by a finger or stylus, can be detected.
A common capacitive touch sensing technique that may be performed on touch screens is mutual capacitance sensing. As shown in FIG. 1A, in mutual capacitance sensing, a drive or transmit signal is applied from a touch screen controller to a subset of the lines referred to as drive or transmit lines, and capacitance values are measured at a subset of the lines referred to as sense or receive lines, with it being understood that in this specific example the receive lines cross the transmit lines in a spaced apart fashion therefrom. Each crossing of transmit line and receive line forms a capacitive node. Since bringing a finger or conductive stylus near the surface of the touch screen changes the local electric field, this causes a reduction in the capacitance between the transmit lines and the receive lines (the “mutual” capacitance), and the capacitance change at every individual capacitive node can be measured to accurately determine the touch location. Therefore, the output of mutual capacitance sensing is a two-dimensional matrix of values, with one value for each capacitive node.
The conductive lines collectively can be referred to as a capacitive touch matrix. One way in which these lines can be arranged is to have the transmit lines be perpendicular to the receive lines and spaced apart from (not co-planar with) the receive lines, as shown in FIG. 1B.
Another way the conductive lines can be arranged is into diamond shapes, as shown in FIG. 1C. Here, the transmit lines and receive lines are diamond shaped, with one (either the transmit lines or receive lines) being located within one plane, and with the other being generally located in the same plane but with a wire or bridge extending through another plane to provide for spaced apart intersections between the transmit lines and receive lines. As can be seen in FIG. 1C, the lines labeled as X-ITO extend within a single plane, while the lines labeled as Y-ITO have portions extending into a second plane to cross the lines labeled as X-ITO.
While the capacitive touch matrix arrangements of FIGS. 1B-1C provide for accurate touch sensing, they have drawbacks in that they can be more expensive to produce than desired, have a lower manufacturing yield than desired, are thicker than desired (due to the capacitive touch matrix requiring more than a single layer), and may lead to the touch screen they are incorporated into having larger bezels than desired. As such, additional development is needed.